1. Field of Invention
The present invention relates to optical multiplexing and demultiplexing devices using a two-dimensional photonic crystal structure, optical communication apparatuses, and optical communication systems.
2. Description of Related Art
Increasing the capacity of communication systems can be advantageous. Thus, the related art includes optical products using a wavelength division multiplexing (WDM) method in which a large amount of information can be multiplexed on a predetermined optical wavelength band and can then be transmitted through optical fibers. In particular, an optical multiplexing and demultiplexing device (referred to as an optical branching and inserting device or an optical add-drop multiplexer in some cases), in which a predetermined signal can be extracted from a multiplexed signal or in which a signal can be added to form a multiplexed signal, can be considered in the related art to be a key device among optical components used for the wavelength division multiplexing system described above.
The related art includes various types of the above optical multiplexing and demultiplexing device, for example, an array waveguide diffraction lattice type, a fiber grating type, and a photonic crystal type. One such optical multiplexing and demultiplexing device is disclosed in Japanese Unexamined Patent application Publication No. 2001-272555. The disclosed device uses a two-dimensional photonic crystal which has a periodic refractive-index distribution structure on a two-dimensional plane, and due to superior wavelength selectivity thereof, this device can be advantageous.